Canon, Nikon, or Sony?

So I've been shooting with an original Canon 5D for the past year now and am looking at upgrading. Currently only have a 50mm 1.8 and an 85mm 1.8 and one flash unit.
Basically I'm looking at some other systems as well as Canon for an upgrade and it's come down to either the Canon 6D, 7D MKII, Sony A7, or the Nikon D610.

I mainly shoot portraits, weddings, and architecture based street photography, so detail tends to trump outright performance. At this point I'm not too heavily invested in Canon so a switch (if worth it) would be doable.

Do NOT change camera systems unless you have a lot of cash laying around not earning interest

You have the beginnings of a good Canon system. Before you decide, just visit the Nikon and Canon websites and see what it will cost you exactly to replace your full frame camera, the two prime lenses and the flash unit.

Usually when a photographer "upgrades" their camera, the keep their old camera as there second or backup camera and continue buying more glass.

The 7D, Mark II is a cropped frame camera.

The Sony A7 series use battery power like a maniac due to the electronic viewfinder vs the optical viewfinders on the other cameras.

Here is a link that you can follow to see how the sensors of those three camera brands compare.

The two lenses you have now are perfect for shooting portraits and weddings (although I would add the 24-70 mm f/2.8 in your mix) Since you are shooting a lot of architecture and street photography, I'm really surprise that you do not have at least one wide angle lens, prime or zoom like one of Canon's EF 16-35 mm or an EF 20 mm

Here is how the sensors of those camera fall when it comes to total performance.

Your 5D -- 121st place
6D -- 44th place
A7 -- 13th place
D610 -- 8th place

If you have the money, the Canon 70D is most likely the best camera you could buy. If you are on a budget, the Nikon D3300 is also a great camera

Pentax!